Method and apparatus for perforating wellbores and casings



July 26, 1960 J. J. UDRY I 2,946,283

METHOD AND APPARATUS FOR PERFORATING WELLBORES AND CASINGS OriginalFiled March 28, 1951 JOHN J: (/DRV INVENTOR.

2,946,283 7 METHOD AND APPARATUS non PERFORATING WELLBORES AND CASINGS.

John J. Udry, Van Nuys', Calif., assignor, bymesne assignments, toBorg-Warner Corporation, Vernon, 'Calih, a corporation of Illinois 1 IContinuation of application Ser. No. 217,967, Mar. 28, 1951. Thisapplication Sept. 2, 1955, Ser. No. 532,148

SClaims. (Cl.102-20l nitcd States 2,946,283 A: Patented July 26,

It is, therefore, one of the primary objects of'the'pres ent inventionto provide a means for Well perforating whereby the wellbore and/orcasing is subjected to'the combined'penetrating action of both a bulletand a shaped charge. I

A further object of the invention is to provide a method and apparatusby which a wellbore formation may be perforated to provide an improvedtype of formation disturbance adjacentthe-penetrated area, partaking ofthe advantages of the effect of both bullet and shaped charge.

With respect to the apparatus itself, it is one of the primary .objectsofthe present invention to provide a novel and improved well perforatinggun by means of which a given point in'the Well casing and/ or formationmay be subjected to the substantially simultaneous penetrating effectofboth a bullet and a shaped charge'jet.

I Q" As' a corollary to the above, it is an object of the present is acontinuation of my copending application SerialNo.

217,967 filed March 28, 1951 now abandoned. j r

As a means of permitting the entrance. and enhancing the flow ofproduction fluid into a cased well, it has'long been conventionalpractice to perforatethe Well'casing in situ within the well borehole ata point in the well opposite the formations from which productionisdesired. .Such perforation was originally accomplished by mechanicallyactuated means lowered into thewell, but this method had, as one of itsseveral disadvantages,,the inability to penetrate the surrounding cementand formatrons. Subsequent practice has been to subject the well casingand the well borehole to the penetrating actionof bullets fired by meansof explosive charges from a perforating gun suspended in the wellborehole, and this had the advantage of not only perforating the wellcasing, but also the surrounding cement and formations to a considerablelateral depth. In more recentdevelopments of perforation by explosiveforce, shaped explosive charges have been used, in which the force ofthe high velocity jet from the shaped charge is alone suflicient toeffect the perforation of both the casing and the surrounding cement andwell formations to considerable lateral depth.

Both bullet perforation and shaped charge perforation for thebefore-mentioned purposes havebeen highly successful and are widelyused, particularly in the oil fields for the simultaneous perforationofwell casings and surrounding bore formations, as well as for theperforation of the surrounding cement with which'thecasing or theseveral concentric strings of casings may be cemented in place in theWell borehole. Each of such methods of perforation has its owncharacteristic advantages and disadvantages. In each case, a singlepenetration is'made into the formation, the depth and contourof whichare determined in part by the physical nature of the formation and inpart by the penetrating characteristics of the bullet or the shapedcharge jet, as the case may be. The resultant formation disturbance atand adjacent'the resultant penetration is in each case individuallytypical of the perforation method selected. I have discovered, however,that, by the combined use of a shaped charge and a penetrating bullet,the character of the penetration and the formation disturbance adjacentthe penetration are different from those produced by either bullet orshaped charge alone. In particular, the flight characteristics of abullet fired in conjunction with the discharge of a shaped charge in themanner herein disclosed are different'frorn those of either a bullet ora shaped chargefired alone, and the resulting character of the formationpenetration is superior in both apparent permeability and porosity ofthe formations so perforated.

invention to provide a gun perforator having meansfor firingsubstantially simultaneously andcoaxially both a bullet and a shapedcharge into and through a single per,- foration made, thereby.

Other objects of the invention'are to provide a novel, simple andimproved gun perforator, the construction and arrangement of whichresult in superior penetrating power.

'These and other objects, advantages, and featuresof novelty of thepresent invention will be evident from a consideration of the followingspecification taken in conjunction with the accompanying drawing.

In the drawing, which illustrates a-preferred. embodiment and mode ofoperation of the invention and in which like reference charactersdesignate the same or similar parts throughout the several views:

.. Figure l is a fragmentary longitudinal elevational view ofth'e gunbody; .and

Figure 2 is an enlarged cross-sectional apparatus taken on line 2-2 ofFigure l.

T he apparatus is as follows:

view of the Referring to the drawing, the general assembly of the bodyof the perforating gun is indicated by the numeral 10. The body 16 ispreferably of cylindrical form, substantially circular in cross-sectionas shown in Figure 2, andof such length as the desired number andlocation of gun units therein may require. In the present disclosure,.only one typical perforating gun unit is illustrated, but it is to be"understood thata plurality of such units may be incorporated in'a singlegun body and may be spaced and arranged along the length thereof asdesired. Frequently, such units are-positioned in spiral arrangementalong the cylindrical gun body, and such is here contemplated. However,since the units may be individually mounted in individual gun bodies, orarranged invarious groups, spacings, and relationships as desired, andsince the present invnt'ionis in no way limited to any particulardisposi: tion, numbenorarrangement of the gun units, a fragmentaryshowing of: the gun body containingonly one typical gun unit is shown;While the body may be formed of shatterable or brittle material, such'ascast iron,

' to disintegrate upondischarge of the units, it is preferably serves asa bullet'propellant charge chamber, being of formed of more durablematerial, such as steel, which will withstand the shock of individual orsimultaneous discharge of the gun units so that it may bereloaded andrepeatedlyused; I

At the location of the gun unit, the cylindrical body -10 istransversely slotted or recessed to form a longitudinal plane surface (11 bounded by top and bottom latere reduced diameter relative to that ofsaid outer portion 13 and forming at the juncture thereof an annularshoulder 19. The outer bore 13 is provided with internal threads 14adapted to threadedly engage external threads 15 of a cylindrical gunbarrel 16, which is thereby screwed into the bore 13 to seat firmlyagainst the shoulder 19'. The barrel 16 is provided with a bullet bore17 extending coaxially therethrough from end to end. An annular recess20 is formed between the thread free rearward extremity of the bulletbarrel 16 and outer bore 13 adjacent the annular shoulder 19, in whichis located an O ring or the like packing means 21. The purpose of thepacking means 21 is to prevent leakage of well fluid and propellantgases between the threads 14, 15 and the propellant charge chamber 18.

When the gun is loaded, as illustrated in Figure 2, a propellant charge.of a suitable powder or other defla-grating or explosive material islocated within the charge chamber 18, as shown at 26, and when ignitedserves to expel a bullet, as shown at 22, outwardly through the bore 17of the barrel 16. The propellant charge is preferably molded,compressed, or otherwise suitably consolidated to form an annular bodyhaving a centrally located opening 28 therethrough. In the present formof the invention, the bullet 22 and its propellant charge 26 may beassembled as a single cartridge unit. The bullet 22 is supported at itsmid-section, partially within the barrel 17 and extending rearwardlytherefrom into the charge chamber 18, by a sealing disc or diaphragm 23,together with a frusto-conical restraining annulus 24, through both ofwhich the bullet may be tight press fitted to be retained until thecartridge is fired. The disc 23 and ring 24 may be separate, but arepreferably securely united as by Welding or the like and, if desired,may be formed as a single integral part. The periphery of the disc 23 isformed with an inwardly or rearwardly directed sealing flange 25 whichfits snugly Within the forward portion of the cylindrical side walls ofthe chamber 18. The inside face of the flange 25 tapers rearwardly awayfrom the body of the disc and receives therein the forward end portionof a cylindrical powder container shell 27 which serves to enclose theannular shaped body of the bullet propellant 26. The central opening 28of the annular propellent charge encircles the inner end of the bullet22.

For igniting the powder 26, an igniter head 30 is located within ashallow recess 31 formed centrally of the rear end wall 32 of the chargechamber 18, the igniter head 30 extending inwardly therefrom into therear portion of the central opening 28 of the propellant charge body 26.An electrically conductive stem 33 is attached to and extends coaxiallyrearwardly from the igniter head 30 through a passage 34 which isprovided with an internal insulating sleeve 35. The outer threaded endof the stem 33 extends into a recess 36 formed in the external wall ofthe body 10 at a point diametrically opposite the surface 11, and isprovided within the recess with a connector means 37 to which may besecured an insulated conductor wire 38 which extends from the saidrecess 36 through a lateral duct 39 to a firing control cable 40contained Within a longitudinal cable recess 41. A nut 42 engages thethreaded outer end of the stud 33 and is secured within the recess 36 byencasement within a sealing plug 43, which in turn is retained andsealed fluidtight within the recess by a convex cover plate 44. By thisarrangement, replacement of the igniter head 30 may be accomplishedafter firing of the gun, by first removing the barrel 16 and thenreaching through the bores 13 and 18 and grasping the igniter head 30with a suitable tool and unscrewing the expanded igniter head and itsstem from the nut 42, and replacing it with a new igniter in the samemanner.

For a more detailed description of the bullet gun perforator portion ofthe apparatus hereinbefore described as suitable in connection with thisinvention, reference 4 may be had to the copending application ofForrest V. Porter, Serial No. 460,086.

The forward or muzzle end of the barrel 16 which is shown as protrudingslightly from the surface 1 1, has formed on it a central boss 45encircling the bullet bore 17. Mounted upon the boss 45 and engaging theannular shoulder formed thereby is a tubular spacer nipple 46.Seated-withinthe outer end of the spacer nipple 46 is the innercylindrical end portion 47 of the container .of a-shapedcharge 48. Thenipple 46 serves to support the inner end of atheshaped charge incoaxial alignment with and in predetermined spaced relation to the outermuzzle end of the barrel bore '17., thus determining the axial spacingof the inner end portion of theshaped charge with respect to the outerend of the barrel and the bullet 22. A suitable detonator cap 49 islocated centrally at the inner end 47 of the shell of the shaped charge48 and in coaxial alignment with the bullet bore 17, in position to bestruck and detonated by impact of the bullet as and when the bullet isfired from the gun barrel 17. The detonator extends through a suitablecentral opening in the end 47 of the shell into the rear portion of theshaped charge explosive.

The shaped charge 48 may have various forms now well known in the art,but .as here illustrated it is contained within a relatively thin shell50 having the beforementioned inner rearward cylindrical portion 47, anintermediate frusto-conical portion 51, and an outer or forwardcylindrical portion 52. The walls of the shell 50, as well as thesurface of the inner end 47, are preferably composed of a frangiblematerial, such as a suitable plastic or like substance, within which ispressed or molded the high explosive material 53 constituting the shapedcharge. The forward end of the body of the explosive 53 is formed with aconcavity 54 preferably conical in shape and preferably covered or linedwith a conical liner 55 made of a suitable metal such as, for example,copper.

The forward end of the outer cylindrical portion 52 of the shell of theshaped charge 48 is supported by, and the charge as a whole is encasedwithin, a relatively thin, approximately hemispherical shaped housing57, preferably made of a frangible material, such as cast iron or thelike. The base of the housing 57 carries a radial flange 58 throughwhich bolts 59 extend into threaded holes in the surface 11 of the gunbody 10 for securing the housing in place upon the surface 11. Anannular groove 60, within which is located an O ring 61 is located underthe flange 58 for providing a fluid-tight seal between the housing andthe surface 11. Within the housing 57 an annular shoulder 62 is providedfor engaging the outer edge of the cylindrical portion 52.of the shell51 of the shaped charge 48 to secure the same in coaxial alignment withthe bullet bore 17 of the gun unit.

For a more detailed description of the general construction andmaterials employed in shaped charges of the type herein described by wayof illustration, reference may be made to the patents to Davis et al.No. 2,399,211 and Muskat et al. No. 2,494,256.

The operation of the apparatus is as follows:

When the well casing or borehole formation is to be perforated, the gunbody is lowered, by means of a conductor cable in a manner Well known inthe gun perforating art, into the well borehole to the depth whereperforation is desired. In the contemplated form of the invention, thebody is, as hereinbefore mentioned, an elongated cylinder carrying orcontaining a plurality of gun units of the type here shown, each unitusually being positioned with its axis directed radially with respect tothe longitudinal axis of the gun body. With the gun body so located, anenergizing electrical impulse is transmitted through the supportingconductor cable and thence by suitable connector means throughconductors 40 and 38 .to and through the stem 33 of the igniter 30, andreturn through ground. The propellant charge 26, being thus ignited,propels the bullet 22 outwardly-at high velocity through the bullet bore17.

As the bullet 22 emerges from the muzzle end of the bore 17 followingthe ignition of the charge 26, its nose strikes the detonator 49,instantly detonating the shaped charge 48. When the charge 48 isdetonated, the housing 57 is disintegrated, and a piercing jet composedof gaseous products of the detonated explosive material therein,together with molten and atomized particles of the conical liner 55, isprojected forwardly in a direction coincident with the axis of thebullet bore, and this jet and the bullet perforate the surroundingcasing or casings, cement, and formation. From a study of casings andformations pierced by such combined action of the bullet and shapedcharge fired in the manner thus described, it appears that the rapiddetonation of the shaped charge is such as to cause the piercing jetthereof to slightly precede the flight of the bullet so as to pierce anycasing present in the well and also to pierce the surrounding formationto considerable depth in advance of the bullet. In any event, thecombined action of the shaped charge jet and the bullet is so nearlysimultaneous as to produce a piercing action superior to that producedby either instrumentality alone or to that produced by the separatesuccessive action of jet and bullet or bullet and jet.

Characteristic of the results thus far obtained by the present method isthe formation of a duct of considerably greater diameter than thatformed by either the bullet-or the shaped charge alone, indicating anapparent spinning or tumbling of the bullet, possibly induced by theshaped charge jet. Such action of the bullet is also indicated bydiscovery of the spent bullet in the test formation in a positionreversed from that in which it was fired. By such wabbling or tumblingaction of the bullet, apparently induced by the action of the shapedcharge jet, a jagged, enlarged bore of apparently superior permeabilitycharacteristics results. From such experiments it appears that, ashereinbefore suggested, the leading portion of the jet precedes thebullet and pierces and displaces sulficient formation to permit tumblingaction of the bullet to be induced by the trailing portion of the jetinto which the bullet enters. However, the invention herein described isnot to be limited in any manner by any theory of its operation.

While the apparatus as herein described has been found to accomplish theobjects of this invention, various modifications thereof may bepossible. For example, modifications of the propellant charges, both forthe bullet and the shaped charge, will probably result in slightvariations in the character of the perforations attained. Likewise,variations in the bullet size and weight, barrel length, bulletrestraint, and the like may also provide other slight variations in theresults obtained. If desired, the shaped charge may be fired by othermeans than the bullet so long as the timing relative to the firing ofthe bullet propellant charge is properly controlled to approximate theconditions obtained by the apparatus herein described. In any event, theprimary inventive concept will be practiced in the approximatelysimultaneous firing of a bullet and a shaped charge coaxially at thesame point in a Well casing or formation.

From the foregoing it will be seen that the present invention provides anovel and improved method of and apparatus for the perforation of wellcasings and/or wellbore formations. In the use of the term well casingsand/ or formations, it is understood that the piercing of pluralconcentric casings is contemplated, as well as the piercing ofcementitious material which may be placed between such concentriccasings or which may be exterior of either a single casing or theoutermost casing of a concentric series thereof.

In the practice of the present invention, both as to method and as toapparatus, it will be understood that numerous changes, modifications,and the full use of equivalents may be resorted to by those skilled inthe art without departure from the scope of the invention as defined inthe appended claims.

Whatis claimed is:

1. A perforating gun comprising: a gun body; a bullet-receiving gun borein said body; a bullet in said gun bore; a charge of propellant powder-'arranged to propel said bullet from the outer end of said gun bore;anoutwardly facing shaped charge on 'saidbody. and positionedinfcoaxial' alignment with' and adjacent the outer end of said gun bore;and a detonator cap detonable by impact of a bullet propelled from saidgun bore and capable upon detonation of detonating said shaped charge,said cap being carried by the rearward end of said shaped charge andpositioned to be actuated by impact from a bullet propelled out of saidbore.

2. A perforating gun comprising: a gun body; a bulletreceiving gun borein said body; a bullet in said bore; a charge of propellant powderarranged to propel said bullet from the outer end of said gun bore; anoutwardly facing shaped charge on said body and positioned in coaxialalignment with and adjacent the outer end of said gun bore and spacedfrom said bullet a portion of the length of said gun bore, the rearwardend of said shaped charge thereby being positioned to be struck by saidbullet when said bullet is propelled out of said bore, the bullet andproducts of said shaped charge being thereby adapted to commingle; and adetonator cap detonable by impact of said bullet and capable upondetonation of detonating said shaped charge, said cap being in therearward end of such shaped charge and positioned to be actuated by theresultant impact from said bullet.

3. In a device of the character described: a gun body; abarrel-receiving bore extending inwardly from an exterior surface of thesaid body; a barrel having a bullet bore therethrough mounted in saidbarrel-receiving bore; an outwardly facing shaped charge positioned incoaxial alignment with and adjacent the outer end of said bullet bore,such shaped charge thereby being adapted to be detonated by impact froma bullet propelled from said bullet bore; a barrel-engaging nipplesupporting the inner end portion of said shaped charge; frangible,fluid-tight enclosing means for the outer end of said barrel, saidshaped charge, and said nipple; means supporting said enclosing means onsaid gun body; and means on said enclosing means supporting the outerend portion of said shaped charge.

4. A perforating gun comprising: a gun body; a bullet receiving gun borein said body; a bullet in said bore at the rearward end thereof; meansincluding a charge of propellant powder arranged to expel said bulletfrom the outer end of said gun bore; an outwardly facing shaped chargeof high explosive positioned in coaxial alignment with and adjacent theouter end of said gun bore and spaced from said bullet a portion of thelength of said gun bore; and a detonator cap detonable by impact of saidbullet and capable upon detonation of detonating said shaped charge,said cap being carried by the rearward end of said shaped charge indetonating relation thereto and positioned to be impacted by said bulletwhen the latter is propelled out of said bore.

5. In a device of the character described: a gun body; abarrel-receiving bore extending inwardly from an exterior surface of thesaid body; a barrel having a bullet bore therethrough mounted in saidbarrel-receiving bore;

an outwardly facing shaped charge positioned in coaxial alignment withand adjacent the outer end of said bullet bore; abullet-impact-sensitive detonator cap capable upon detonation ofdetonating said shaped charge, said cap being carried by the rearwardend of said shaped charge in detonating relation thereto and in coaxialalignment With said. bullet bore, said cap thereby being adapted to bedetonated by impact from a bullet propelled from said bullet bore; abarrel-engaging nipple supporting the inner end portion of said shapedcharge; frangible, fluidtight enclosing means for the outer end of saidbarrel,

References Cited in the file of this patent UNITED STATES PATENTS120,963 Gomez Nov. 14, 1871 10 8 Bolton .L Dec. 16, 1941 Foster Jan. 5,1943 Davis Aug. 10, 1948 Phillips Aug. 25, 1953 Sweetman May 25, 1954Sweetman Feb. 14, 1956 Moses Oct. 15 1957 FOREIGN PATENTS France July12, "1950

